An American civilian contractor working in Iraq was killed Tuesday when a bomb exploded under his truck north of Tikrit.

A U.S. military spokesman says the contractor, an employee of the Kellogg, Brown and Root company, had been traveling in a five-vehicle convoy when it was attacked.

The company, a subsidiary of energy services giant Halliburton, has been working at a refinery and pipeline terminus, 50 kilometers north of Tikrit. Halliburton, once headed by Vice President Dick Cheney, has major reconstruction contracts in Iraq and Afghanistan.

The military spokesman says the contractor died after being taken to a U.S. military field hospital in the area.

Meanwhile, U.S. military officials in Iraq also report soldiers hunting Saddam Hussein loyalists have detained nine people, including four suspected fugitives, in the Tikrit area.

They say the nine detained were members of either the banned Baath party or the deposed Iraqi leader's dreaded Fedayeen militia.

Elsewhere in Iraq, a spokesman for coalition forces says, the troops have carried out over two dozen raids over the past 24 hours, making numerous arrests and confiscating illegal weapons. In the northern town of Mosul, the spokesman said troops also found a cache of more than 50 mortar rounds.

In another development, the U.S.-led coalition is warning Iraqis to refrain from staging violent demonstrations. The AFP news agency reports that coalition authorities have displayed dozens of posters near their headquarters in Baghdad, warning that coalition troops will not tolerate violent protests.